Interest in maturing the capabilities of small satellite platforms (e.g., mass less than ˜20 kg and volume less than ˜10,000 cm3) has grown dramatically in recent years. Initial efforts to develop small spacecraft were primarily academic efforts to reduce the resources required for access to space. Now, small spacecraft, including the CubeSat standard, are attracting significant interest for use in missions that would have previously been reserved for larger spacecraft. This increased interest is driving the need to expand the capabilities of subsystems on small satellites, such as communications systems, while keeping within the significant constraints imposed by the limited size and mass of the platform.
Large-scale implementation of space-based laser communications systems has been actively discussed for decades. To date, however, specific implementations of this technology have been limited to a handful of discrete demonstrations using large spacecraft platforms. The slow progress toward main-stream adoption of space-based laser communications, even on large spacecraft, has been constrained by available platforms willing to experiment with the technology. While limited in complexity and number, there has been a steady string of optical communication demonstrations using orbiting assets. For example, in 1992, the GOPEX experiment successfully transmitted laser pulses from Earth which were detected by a receiver aboard the Galileo probe en-route to Jupiter while at a range of approximately 6 million km. In 2005, the MESSENGER spacecraft, while en-route to Mercury, participated in the first two-way interplanetary communications link through use of the on-board laser-altimeter and NASA's Goddard Geophysical Astronomical Observatory at a distance of 24 million km. The European Space Agency (ESA) also conducted an experiment between the Artemis spacecraft (a GEO telecommunications satellite) and the French SPOT-4 spacecraft in LEO using two optical communications SILEX (Semi-conductor Inter-satellite Link Experiment) terminals, one on each spacecraft. In 2001, this inter-satellite system was first successfully demonstrated at a range of 36,500 km and a data rate up to 50 Mb/s. This same Artemis SILEX terminal was subsequently used in 2006 to demonstrate a similar data transmission rate to a terminal on an aircraft in flight. In 2005, The Japan Aerospace Exploration Agency (JAXA) launched the OICETS (Optical Inter-Orbit Communications Engineering Test Satellite), also known as Kirari. This platform demonstrated an inter-satellite link to ESA's Artemis spacecraft shortly after launch, and was subsequently used in 2006 and beyond to demonstrate optical communications capability to several ground stations. More recently, a bi-directional inter-satellite link was demonstrated in 2008 between the TESAT-built German TerraSAR-X satellite and a corresponding TESAT laser communications terminal aboard the US NFIRE spacecraft at a distance of 5,000 km and a rate of 5.5 Gbps.
Previous laser communications experiments have universally been demonstrated with a large spacecraft platform as host. To date, there has been little work in the area of miniaturizing this technology into a robust and reliable system for micro-satellites or nano-satellites.